JPS6137618B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor comprising a photosensitive layer made of an organic photoconductive compound. Conventionally, electrophotographic photoreceptors having a photosensitive layer containing as a main component an inorganic photoconductor such as selenium, subsalt oxide, or cadmium sulfide are widely known. However, these are not necessarily satisfactory in terms of properties such as thermal stability, durability, and moisture resistance.
Moreover, there are also problems in manufacturing and handling due to toxicity. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, easy to handle, and generally selenium photoreceptors, etc. It has many advantages, such as superior thermal stability, and has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is the most well-known such organic photoconductive compound, and 2.
Electrophotographic photoreceptors having a photosensitive layer containing as a main component a charge transfer complex formed with a Lewis acid such as 4,7-trinitro-9-fluorenone have already been put into practical use. On the other hand, electrophotographic photoreceptors are known that have a laminated type or dispersion type functionally separated photosensitive layer in which the carrier generation function and the carrier transport function in the photoconductive photosensitive layer are assigned to separate substances, respectively. For example, electrophotographic photoreceptors have been put into practical use that have a photosensitive layer that combines a carrier generation layer made of an amorphous selenium thin layer and a carrier transport layer made of poly-N-vinylcarbazole. However, since poly-N-vinylcarbazole lacks flexibility, its coating is hard and brittle and prone to cracking and peeling, and therefore electrophotographic photoreceptors using it have poor durability. Moreover, if a plasticizer is added to improve this drawback, the residual potential will increase when subjected to the electrophotographic process, and as the material is used repeatedly, the residual potential will increase and gradually fog will occur in the copied image. It has some drawbacks. Furthermore, since low molecular weight organic photoconductive compounds generally do not have film-forming ability, they are used in combination with any binder. Therefore, it is preferable in that the physical properties or electrophotographic properties of the film can be controlled to some extent by selecting the type and composition ratio of the binder used, but it is preferable that the film has high compatibility with the binder. The types of organic photoconductive compounds that have
In reality, there are not many materials that can be used in the composition of the photosensitive layer of an electrophotographic photoreceptor. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole described in U.S. Pat. No. 3,189,447 is usually preferably used as a material for the photosensitive layer of an electrophotographic photoreceptor. Therefore, when it is mixed with a binder such as polyester or polycarbonate in the ratio required to obtain favorable electrophotographic properties to form a photosensitive layer, At temperatures above 50°C, oxadiazole crystals begin to precipitate, resulting in a disadvantage that electrophotographic properties such as charge retention and sensitivity deteriorate. On the other hand, the diarylalkane derivatives described in U.S. Pat.
When used in the construction of a photosensitive layer of an electrophotographic photoreceptor of a repetitive transfer type in which charging and exposure are repeated, it has the disadvantage that the sensitivity of the photosensitive layer gradually decreases. In addition, the structural formula described in Japanese Patent Application Laid-Open No. 55-46760 An electrophotographic photoreceptor constructed using the hydrazone compound represented by as a carrier transport material is not fully satisfactory in terms of sensitivity, residual potential characteristics, etc., and the sensitivity gradually decreases as the photoreceptor is used repeatedly. However, since the residual potential increases, the durability is poor. The reality is that an organic photoconductive compound having practically preferable characteristics for producing an electrophotographic photoreceptor has not yet been found. An object of the present invention is to provide an electrophotographic photosensitive layer comprising a photosensitive layer containing a novel organic photoconductive compound that has excellent compatibility with a binder, is stable against heat and light, and has excellent carrier transport ability. It's about offering your body. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and low residual potential. Still other objects of the present invention include charging, exposing, developing,
To provide an electrophotographic photoreceptor of excellent durability that exhibits stable characteristics over a long period of time and has little fatigue deterioration due to repeated use when used as a repeat transfer type electrophotographic photoreceptor in which a transfer process is repeatedly performed. It is in. As a result of intensive research to achieve the above object, the present inventors discovered that the object could be achieved by using a specific diazepine derivative as a material constituting the photosensitive layer of an electrophotographic photoreceptor, and completed the present invention. This is what I did. The above object is achieved by providing on a conductive support a photosensitive layer containing at least one diazepine derivative represented by the following general formula [], [] or []. (In each formula, R ₁ , R ₂ , and R ₃ each represent a substituted or unsubstituted aryl group or a substituted or unsubstituted styryl group, and R ₄ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. ) That is, in the present invention, the general formula [],
A diazepine derivative represented by [ ] or [ ] is used as a photoconductive substance to form a photosensitive layer of an electrophotographic photoreceptor, or the diazepine derivative is used as a carrier transport substance by focusing on its excellent carrier transport ability. , and a carrier-generating substance to form a photosensitive layer of a so-called functionally separated photoreceptor in which carrier generation and transport are performed by separate substances, respectively. As a result, it is possible to provide an electrophotographic photoreceptor that has excellent coating physical properties, exhibits little fatigue deterioration even when used repeatedly, and can exhibit stable characteristics. Specific examples of the diazepine derivatives represented by the general formulas [], [], and [] that can be effectively used in the present invention include those having the structural formulas shown below, but of course they are not limited to these. It is not something that will be done. The above diazepine derivatives can be easily synthesized by known methods. For example, literature
Helv.Chim.Acta., Volume 39 (1956), Page 207,
Can.J.Chem., Vol. 52 (1974), p. 2798, or
Acta.Chem.Scand., Vol. 23 (1969), No. 3125,
It can be synthesized according to the following reaction formula using methods described elsewhere. Here, R ₁ , R ₂ , R ₃ and R ₄ in the formula represent the same as shown for the above general formulas [], [] and [], respectively, and X ^- is ClO ₄ ^- , BF ₄ ^- ,
Represents a counterion such as PF ₆ ^- . Next, a typical method for synthesizing the diazepine derivative used in the present invention will be specifically explained. Synthesis Example 1 (Synthesis of Exemplified Compound []-2) 4-(p-dimethylaminophenyl)-2.6-
Diphenylthiopyrylium perchlorate 4.7g
(0.01 mol) of fine powder was mixed with hydrazine hydrate (100
%) in 50 ml portions and stir at room temperature for 18 hours. The formed precipitate is collected by filtration, thoroughly washed with methanol, dried, and then recrystallized with acetonitrile. The yield in this method is 3.1 g (yield 84.9%), and the melting point of the target product is 217-218°C. Synthesis Example 2 (Synthesis of Exemplified Compound []-1) 3,5,7-triphenyl-1,2(4H)-diazepine (Exemplified Compound []-1) 3.8 g (0.012
A mixture of 120 ml of iodomethyl mol) and 5 g of sodium hydroxide is stirred at room temperature for 24 hours, the formed precipitate is removed by filtration, and the filtrate is separated and purified by silica gel column chromatography. The yield in this method is 2.7 g (yield: 67.5%), and the melting point of the target product is 117-118.5°C. Diazepine derivatives such as those mentioned above have almost no photosensitivity to light in the visible region, and therefore it is necessary to perform a sensitization treatment in order to enable the exposure process to be performed with visible light. It is. Various methods have been proposed for sensitizing organic photoconductivity, and the first method is to perform spectral sensitization (dye sensitization) by adding an organic dye. A second method is to add a substance that forms a charge transfer complex, and since the diazepine derivative is an electron-donating substance in the present invention, this substance can be an electron-accepting substance. preferable.
In the present invention, when the diazepine derivative is used as a carrier transport substance, it may be combined with a carrier generating substance having the function of absorbing visible light and generating charged carriers, such as another organic dye or pigment or an inorganic photoconductive substance. By using a functionally separated photoreceptor, a de facto sensitization process can be performed. All of the sensitization methods described above are effective for the diazepine derivative used in the present invention, and an appropriate method may be selected from various other conditions. Typical examples of organic dyes for spectral sensitization used when sensitization is carried out by spectral sensitization are as follows. (A-1) Triphenylmethane dyes such as methyl violet, crystal violet, and malachite green (A-2) Xanthene dyes such as erythrosine and rose bengal (A-3) Thiazine dyes such as methylene blue and methylene green (A-4) Oxazine dyes such as caprylic blue and Meldora blue (A-5) Cyanine dyes such as thiacyanine and oxacyanine (A-6) Styryl dyes such as p-dimethylaminostyrylquinoline (A-7 ) Pyrylium salt dyes such as pyrylium salts, thiapyrylium salts, benzopyrylium salts, and benzothiapyryllium salts (A-8) 3,3'-dicarbazolylmethane dyes, which also form charge transfer complexes with the diazepine derivatives mentioned above. Examples of preferable electron acceptors include 2,4,7-trinitrofluorenone,
Lewis acids such as 2,4,5,7-tetranitrofluorenone, chloranil, and tetracyanoxydimethane can be mentioned. Furthermore, as carrier-generating substances used when constructing a functionally separated photoreceptor, various dyes mentioned above as organic dyes for spectral sensitization can be effectively used, but in addition, there are the following: . (B-1) Azo dyes such as monoazo dyes, bisazo dyes, and trisazo dyes (B-2) Perylene dyes such as perylenic anhydride and perylenic acid imide (B-3) Indicoid dyes such as indico and thioindico ( B-4) Polycyclic quinones such as anthraquinone, pyrenequinone, and flavanthrones (B-5) Quinocridone dyes (B-6) Bisbenzidazole dyes (B-7) Indanthrone dyes (B-8 ) Squarelylium pigments (B-9) Phthalocyanine pigments such as metal phthalocyanine and non-metal phthalocyanine (B-10) Selenium and selenium alloys (B-11) Inorganic photoconductors such as cadmium sulfide and cadmium selenide (B- 12) Eutectic complex formed from pyrylium salt dye, thiapyrylium salt dye and polycarbonate In addition to the above sensitization methods, methods using chemical sensitizers can also be effectively used. Since the diazepine derivative used in the present invention does not have the ability to form a film by itself, the photosensitive layer is constructed by combining various binders. Any binder can be used here, but it is preferable to use a film-forming polymer that is hydrophobic, has a high dielectric constant, and is electrically insulating. Examples of such high molecular weight polymers include, but are not limited to, the following. (C-1) Polycarbonate (C-2) Polyester (C-3) Methacrylic resin (C-4) Acrylic resin (C-5) Polyvinyl chloride (C-6) Polyvinylidene chloride (C-7) Polystyrene (C -8) Polyvinyl acetate (C-9) Styrene-butadiene copolymer (C-10) Vinylidene chloride-acrylonitrile copolymer (C-11) Vinyl chloride-vinyl acetate copolymer (C-12) Vinyl chloride-acetic acid Vinyl-maleic anhydride copolymer (C-13) Silicone resin (C-14) Silicone-alkyd resin (C-15) Phenol-formaldehyde resin (C-16) Styrene-alkyd resin (C-17) Poly-N -Vinylcarbazole These binders can be used alone or in a mixture of two or more. To explain the mechanical structure of the electrophotographic photoreceptor of the present invention, in one example of the present invention, as shown in FIGS. Carrier generation layer 2
and a carrier transport layer 3 containing the aforementioned diazepine derivative as a main component of the carrier transport substance. Figures 3 and 4
As shown in the figure, this photosensitive layer 4 is formed on a conductive support 1
It may be provided through an intermediate layer 5 provided above. When the photosensitive layer 4 has a two-layer structure in this manner, an electrophotographic photoreceptor having the best electronic properties can be obtained. Further, in the present invention, as shown in FIGS. 5 and 6, a photosensitive layer 4 comprising a carrier-generating substance 7 in the form of fine particles dispersed in a carrier-transporting layer 6 containing the carrier-transporting substance as a main component is provided. , may be provided directly on the conductive support 1 or via an intermediate layer 5. Preferable results can also be obtained by adding a sensitizing dye or a Lewis acid to the diazepine derivative to form a single photosensitive layer without using a carrier-generating substance. Here, when the photosensitive layer 4 has a two-layer structure, which of the carrier generation layer 2 and the carrier transport layer 3 is used as the upper layer is determined depending on whether the charging polarity is selected as positive or negative. That is, when forming a negatively charged photosensitive layer, it is advantageous to use the carrier transport layer 3 as an upper layer, since the diazepine derivative in the carrier transport layer 3 is a substance having a high transport ability for holes. Because there is. Further, the carrier generation layer 2 constituting the photosensitive layer 4 having a two-layer structure can be applied directly to the conductive support 1 or the carrier transport layer 3, or if necessary, after providing an intermediate layer such as an adhesive layer or a barrier layer. It can be formed by the following method. (1) Vacuum evaporation method (2) Method of applying a solution of a carrier-generating substance dissolved in a suitable solvent (3) A method in which the carrier-generating substance is made into fine particles in a dispersion medium using a ball mill, homomixer, etc. A method of coating a dispersion obtained by mixing and dispersing with a binder according to the method. The thickness of the carrier generation layer 2 formed in this way is preferably 0.01 to 5 microns,
More preferably, it is 0.05 to 3 microns. Further, the thickness of the carrier transport layer 3 can be changed as necessary, but it is usually preferably 5 to 30 microns. The composition ratio in this carrier transport layer 3 is 0.8 to 4 parts by weight of the binder to 1 part by weight of the carrier transport material whose main component is the diazepine derivative described above.
It is preferable to use the binder in parts by weight, but when forming the photosensitive layer 4 in which a fine powder carrier-generating substance is dispersed, the binder should be used in an amount of 5 parts by weight or less per 1 part by weight of the carrier-generating substance. is preferred.
Further, when the carrier generation layer 2 is configured as a dispersed layer using a binder, it is preferable to use the binder in an amount of 5 parts by weight or less per 1 part by weight of the carrier generation substance. The conductive support 1 used in the construction of the electrophotographic photoreceptor of the present invention may include a metal plate, a conductive polymer, a conductive compound such as indium oxide, etc.
Alternatively, paper, plastic film, etc., which have been made conductive by coating, vapor depositing, or laminating a thin layer of metal such as aluminum, palladium, or gold, may be used. The intermediate layer 5 such as a binding layer or barrier layer may be made of an organic polymer such as gelatin, casein, starch, polyvinyl alcohol, vinyl acetate, ethyl cellulose, or carboxymethyl cellulose, in addition to the polymer used as the binder. Alternatively, aluminum oxide or the like is used. The electrophotographic photoreceptor of the present invention has the above-described structure, and as is clear from the examples described later, it has excellent charging characteristics, sensitivity characteristics, and image forming characteristics, and is particularly suitable for repeated transfer electrophotography. It also shows little fatigue deterioration and excellent durability. Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited thereto. Example 1 Selenium was evaporated onto a conductive support consisting of a polyester film laminated with aluminum foil to form a carrier generating layer with a thickness of 0.5 microns. Next, 6 parts by weight of Exemplified Compound []-2 and 10 parts by weight of polycarbonate "Panlite L-1250" (manufactured by Teijin Kasei) were added to 1,2-dichloroethane.
90 parts by weight, and the film thickness after drying this solution is
A carrier transport layer was formed by coating to a thickness of 11 microns, and an electrophotographic photoreceptor of the present invention was prepared. The electrophotographic properties of this electrophotographic photoreceptor were measured by a dynamic method using an electrostatic copying paper tester "SP-428 model" (manufactured by Kawaguchi Electric Seisakusho).
That is, the surface of the photosensitive layer of the photoreceptor was charged with a voltage of -6.0KV.
The surface potential V _A when charged for 5 _seconds at exposure amount)

[Formula] and the surface potential (residual potential) V _R after exposure with an exposure amount of 30 lux·sec were determined. In addition, similar measurements were repeated 100 times.
The results are shown in Table 1.

[Table] As is clear from this table, the electrophotographic photoreceptor of the present invention exhibits extremely small changes in each characteristic even after the 100th measurement, and stable characteristics can be obtained. Comparative Example 1 Exemplary compound []-
Instead of 2, the structural formula A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that N-phenylcarbazole represented by was used, and the same measurements were performed. The results are shown in Table 2.

[Table] This comparative electrophotographic photoreceptor has extremely inferior characteristics and cannot be used for practical use as an electrophotographic photoreceptor.
It was canceled after only one session. Example 2 Vinyl chloride-vinyl acetate-maleic anhydride copolymer ``Eslec'' was deposited on a conductive support consisting of a polyester film laminated with aluminum foil.
MF-10'' (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.05 microns, and on top of that, dibromoanthrone ``Monolite Red 2Y'' CI No. 59300.
(manufactured by ICI) was vapor-deposited to form a carrier generation layer with a thickness of 0.5 micron. Next, exemplified compound []-
6 parts by weight of 11 and polycarbonate "Panlite L"
-1250" (manufactured by Teijin Chemicals) 10 parts by weight and 1.2-
A carrier transport layer was formed by dissolving this solution in 90 parts by weight of dichloroethane and applying this solution to a film thickness of 11 microns after drying, thereby producing an electrophotographic photoreceptor of the present invention. The same measurements as in Example 1 were performed on this electrophotographic photoreceptor. The results are shown in Table 3.

[Table] This electrophotographic photoreceptor was also used in the electrophotographic copying machine "U".
-Bix2000R (manufactured by Konishi Roku Photo Industry Co., Ltd.) and conducted a copying test, we were able to obtain a copy image that was faithful to the original, had high contrast, and excellent gradation, and was copied 5,000 times. In some cases, good copy images were obtained as in the initial stage. Furthermore, measurements similar to those in Example 1 were performed on the electrophotographic photoreceptor that had been copied 5,000 times, and the results shown in Table 4 were obtained.

[Table] Comparative Example 2 Exemplary compounds []- as carrier transport substances
11 instead of structural formula A comparative electrophotographic photoreceptor was produced in the same manner as in Example 2, except that the triazine derivative represented by was used. When the same measurements as in Example 1 were performed on this comparative electrophotographic photoreceptor, the results shown in Table 5 were obtained.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention according to Example 2 is extremely excellent in charge retention, sensitivity, residual potential, and stability when repeatedly used. On the other hand, the comparative electrophotographic photoreceptor according to Comparative Example 2 has extremely low sensitivity and poor stability when repeatedly used, so that it can hardly be put to practical use. Examples 3 to 10 Exemplary compounds []- as carrier transport substances
4, []-8, []-2, []-12, []-16
,
A total of 8 types of electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 2, except that []-8, []-12, and []-13 were respectively used, and each of them was prepared in the same manner as in Example 1. The initial characteristics were measured. The results are shown in Table 6.

[Table] Example 11 On the conductive support provided with the intermediate layer used in Example 2, the structural formula A mixed solvent prepared by mixing 1 part by weight of the bisazo pigment represented by ethylenediamine, n-butylamine, and tetrahydrofuran in a ratio of 1.2:1.0:2.2.
140 parts by weight, and the resulting solution was coated to form a carrier generation layer so that the film thickness after drying was 0.3 microns, and then exemplified compound []-11
6 parts by weight of methacrylic resin "Acrypet"
(Manufactured by Mitsubishi Rayon Co., Ltd.) A coating solution prepared by dissolving 10 parts by weight of 1,2-dichloroethane in parts by weight of 1,2-dichloroethane was applied to a film thickness of 12 microns after drying to form a carrier transport layer. An inventive electrophotographic photoreceptor was produced. When the initial characteristics of this electrophotographic photoreceptor were measured in the same manner as in Example 1, it was found that V _A
=-1074(V),

[Formula] V _R =0 (V). Furthermore, when a copying test similar to that in Example 2 was conducted on this electrophotographic photoreceptor, a copied image faithful to the original image, with high contrast, and excellent gradation was obtained, and when copying was repeated 5000 times, Also, excellent copy images similar to those obtained in the initial stage were obtained. Example 12 N·N′-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimide “Paliogen Maroon 3920” was deposited on the conductive support provided with the intermediate layer used in Example 2. (CINo.71130
(manufactured by BASF) was vapor-deposited to form a carrier generation layer with a thickness of 0.4 microns. Next, exemplified compounds []
-6 parts by weight of 7 and polyester “Byron 200”
(manufactured by Toyobo Co., Ltd.) in 90 parts by weight of 1,2-dichloroethane, and this solution was applied to form a carrier transport layer so that the film thickness after drying was 13 microns. A photographic photoreceptor of the present invention was prepared. When the initial characteristics of this electrophotographic photoreceptor were measured in the same manner as in Example 1, it was found that V _A
=-1190(V),

[Formula] V _R =-8 (V). Further, when a copying test similar to that in Example 2 was conducted on this electrophotographic photoreceptor, good copied images were still obtained even after the number of copies reached 5000 times. Example 13 As a carrier generating substance, the structural formula Example 11 except that the bisazo pigment shown in was used.
An electrophotographic photoreceptor of the present invention was prepared in the same manner as in Example 1, and its initial characteristics were measured in the same manner as in Example 1. As a result, V _A =-1022 [V),

[Formula] V _R =-5 (V). Example 14 A 0.1 micron thick intermediate layer made of polyester "Vylon 200" (manufactured by Toyobo Co., Ltd.) was provided on a conductive support made of polyester film laminated with aluminum foil, and 4-(p-dimethylaminophenyl )-2,6-diphenylthiopyrylium perchlorate 1 part by weight dichloromethane 130%
10 parts by weight of polycarbonate "Iupilon S-1000" (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 6 parts by weight of exemplified compound []-14 were added and dissolved, followed by thorough stirring. A photosensitive layer was formed by coating the coating liquid on the intermediate layer so that the film thickness after drying was 12 microns, thereby producing an electrophotographic photoreceptor of the present invention. Measurements were performed on this electrophotographic photoreceptor in the same manner as in Example 1. The results are shown in Table 7.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention has excellent properties such as charge retention, sensitivity, and residual potential, and is also extremely stable when used repeatedly. .

[Brief explanation of the drawing]

FIGS. 1 to 6 are explanatory diagrams of mechanical configuration examples of the electrophotographic photoreceptor of the present invention, respectively. 1... Conductive support, 2... Carrier generation layer,
3...Carrier transport layer, 4...Photosensitive layer, 5...Intermediate layer, 6...Carrier transport layer, 7...Carrier generating substance.

Claims (1)

[Scope of Claims] 1 Comprising an electrically conductive support and a photosensitive layer provided on the electrically conductive support, the photosensitive layer comprising a diazepine derivative represented by the following general formula [], [] or []. An electrophotographic photoreceptor characterized by containing at least one type of photoreceptor. (In each formula, R ₁ , R ₂ , and R ₃ each represent a substituted or unsubstituted aryl group or a substituted or unsubstituted styryl group, and R ₄ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. 2. The layer containing the diazepine derivative constitutes a carrier transport layer, and the photosensitive layer is constituted by a laminate of the carrier transport layer and the carrier generation layer. The electrophotographic photoreceptor described in . 3. The electrophotographic photoreceptor according to claim 1, wherein the layer containing the diazepine derivative contains a carrier generating substance, and the photosensitive layer is constituted by this layer.